There's a belief that if you're looking for water in the desert you can split open a large cactus and drink the water inside. That may be true, except that if you've found a barrel cactus, you've got to be careful, because only one species, the fishhook barrel cactus (Ferocactus wislizeni), can quench your thirst.

Other barrel cactus contain toxins that give you diarrhea and make you vomit, which can kill you if you're dehydrated and lost in the desert.

Also, the barrel cactus pictured above are designed for comfort, not pain. They're actually a sofa designed by Maurizio Galante, with a cactus photo printed on the fabric.